greybus: endo: drop redundant prefixes from sysfs basenames

This commit:
    7e761e2 endo: rework some attributes
added a new "endo_id" attribute, located under a new "Endo"
directory in sysfs.  The resulting path looks like:
    Documentation/sysfs/endo-TYPE/Endo/endo_id
There's no need to have a separate "Endo" subdirectory to contain
Endo-specific attributes.

That commit also added "svc_" to some other paths related to the
SVC, like:
    Documentation/sysfs/endo-TYPE/SVC/svc_version
The additional "svc_" is redundant.

This patch retouches those paths a bit, mainly to remove some
redundancy.  It also makes the pathname components all lower case.
As a result, the above two paths now look like:
    Documentation/sysfs/endo-TYPE/id
    Documentation/sysfs/endo-TYPE/svc/version

All other Endo sysfs files are updated similarly.

Signed-off-by: Alex Elder <elder@linaro.org>
Reviewed-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>